For example, this invention relates to an image processing circuit for effecting an image process of a plurality of processing steps, an image processing apparatus such as an image forming apparatus including the image processing circuit, for printing an image read by a scanner by use of a printer and a control method for the image processing circuit.
Conventionally, an image forming apparatus such as a digital copying machine includes an image processing LSI used as an image processing circuit for effecting an image process of a plurality of processing steps. A common clock is always supplied to an internal circuit of the image processing LSI during the image data processing operation irrespective of the contents of data.
For example, image data processed by the digital copying machine contains data having low-level pixel values of a white ground or the like in many cases. When such image data is processed, particularly, upper bits of data of pixel values (density values) are practically kept at the same value for a long period of time.
However, the conventional image processing circuit is operated only by one common clock for all of the bits. Therefore, the clock is always supplied for the upper bits whose pixel values are kept unchanged in practice for a long period of time, thereby making it difficult to attain the low power consumption of the image processing LSI.